1. The workers built this house in 1998.

`to` This house was built by the workers in 1998.

2. Hoa bought the flowers in the market yesterday. 

`to` The flowers were bought by Hoa in the market yesterday. 
3. They gave the winner a nice prize.             

`to` The winner was given a nice prize by them.

4. The policeman asked her a lot of questions. 

`to` She was asked a lot of questions by the policeman.
5. Nobody showed her the way to the club.  

`to` She wasn't shown the way to the club.  
6. Nam and his friends swept the street. 

`to` The street was swept by Nam and his friends.

CT: bị động QKĐ: S+ was/ were+ Vp2+ by O.

`1` The workers built this house in `1998.`

`=>` This house was built by the workers in `1998.`

`2` Hoa bought the flowers in the market yesterday. 

`=>` The flowers were bought by Hoa in the market yesterday. 
`3` They gave the winner a nice prize.             

`=>` The winner was given a nice prize by them.

`4` The policeman asked her a lot of questions. 

`=>` She was asked a lot of questions by the policeman.
`5` Nobody showed her the way to the club.  

`=>` She wasn't showed the way to the club.  
`6` Nam and his friends swept the street. 

`=>` The street was swept by Nam and his friends.

Câu bị động thì Qúa Khứ Đơn:

`-` S+ V-ed/ V2+ O.

`=>` S+ was/ were+ Vpp+ by O.